Lead researcher, Dr Robert Maher, UCL Electronic & Electrical Engineering, said: “For comparison this is almost 50,000 times greater than the average speed of a UK broadband connection of 24Mbit/s, which is the current speed defining ‘superfast’ broadband.”
The team determined the best way of encoding information in optical signals, taking into account the limitations of the transmitter and receiver. They then applied coding techniques commonly used in wireless communications, but not yet widely used in optical communications, to ensure the transmitted signals are adapted to distortions in the system electronics.
The researchers custom built an optical communication system with 15 channels, each carrying an optical signal of different wavelength, were modulated using the 256QAM format typically used in cable modems, combined and sent to a single optical receiver for detection. By grouping the channels together, the team created a ‘super-channel’ which although not yet commercially available, is believed to be a way forward for the next generation of high-capacity communication systems.
Dr Maher explained: “Using high-bandwidth super-receivers enables us to receive an entire super-channel in one go. Super-channels are becoming increasingly important for core optical communications systems, which transfer bulk data flows between large cities, countries or even continents.”
He added: “However, using a single receiver varies the levels of performance of each optical sub-channel so we had to finely optimise both the modulation format and code rate for each optical channel individually to maximise the net information data rate. This ultimately resulted in us achieving the greatest information rate ever recorded using a single receiver.”
In this study, the researchers connected the transmitter directly to the receiver to achieve the maximum data rate. They will now test the system and measure the achievable data rates in a long distance transmission scenario where optical signals can become distorted as they travel through thousands of kilometres of optical fibres.
